1. Field
This patent application relates to a digital video apparatus, and more particularly to a digital video apparatus which stably detects its status of connection to a peripheral apparatus.
2. Description of Related Art
A conventional digital video apparatus includes a digital video encoder and a digital to analog converter (DAC).
The digital video encoder generates three digital television signals of a luminance signal Y, a chrominance signal C, and a composite signal YC from digital primary color signals of R (red), G (green), and B (blue), or digital signals of Y (luminance signal), Cb (blue color difference signal), and Cr (red color difference signal).
The DAC converts the digital luminance signal Y, the digital chrominance signal C, and the digital composite signal YC to an analog luminance signal Y, an analog chrominance signal C, and an analog composite signal YC, and outputs these analog video signals.
The digital video encoder converts a digital video signal taken by a digital video apparatus such as a digital camera to an analog video signal. The analog video signal is transmitted to and played on a peripheral apparatus such as a monitor television.
The digital video apparatus and the peripheral apparatus such as a monitor television, which is detachable from the digital video apparatus, communicate signals such as a video signal with each other.
The digital video apparatus including the digital video encoder detects a connection status of the peripheral apparatus such as a monitor television to the digital video apparatus. The above-mentioned digital video apparatus can save its power consumption by controlling outputs of the digital video encoder or the like based on the detected connection status. Power saving is a critical matter particularly for a battery-powered portable type digital video apparatus.
An exemplary conventional detection circuit which detects a connection status of a peripheral apparatus such as a monitor television to the digital video apparatus is illustrated in FIG. 1.
As illustrated in FIG. 1, the conventional detection circuit includes a resistor Rd, a resistor Re, a resistor Rt, a connector Tt, a comparator 1, a resistor Rs, a power source Vs, a coupling capacitor Ct, and an amplifier At.
In the conventional detection circuit, the comparator 1 compares a voltage at a connection point between the resistor Rd and the resistor Re (e.g, Re=2×Rd), and a voltage at a connection point between the resistor Rt and the connector Tt to detect a connection status at the connector Tt. The comparator 1 outputs a high level signal when the peripheral apparatus such as a monitor television is connected to the connector Tt.
The conventional detection circuit of the digital video apparatus has a video signal output terminal, and determines whether the peripheral apparatus such as a monitor television is connected to the video signal output terminal of the digital video apparatus.
Specifically, a resistor is provided to a terminal of the digital video apparatus, and pulled up to a power source. The resistor has an ohmic value which is significantly larger than that of a resistor provided to the monitor television and connected to a ground. For example, the resistor provided to the terminal of the digital video apparatus has about one mega ohms, and the resistor of the monitor television has 75 ohms.
When the monitor television is connected to the terminal of the digital video apparatus, a voltage, determined by a voltage dividing ratio of the resistor of the monitor television having 75 ohms and the resistor at the terminal of the digital video apparatus having about one mega ohms, is generated at the terminal of the digital video apparatus.
The conventional detection circuit detects a voltage change at the terminal of the digital video apparatus, and can detect a connection status of the peripheral apparatus such as a monitor television to the digital video apparatus.
The above-mentioned configuration of the conventional detection circuit, which detects a voltage change determined by a voltage dividing ratio of resistors, can stably detect the connection status of the peripheral apparatus such as a monitor television to the digital video apparatus when the digital video apparatus does not output a video signal.
However, when the digital video apparatus outputs a video signal, the above-mentioned configuration of the conventional detection circuit cannot stably detect the connection status of the peripheral apparatus such as a monitor television to the digital video apparatus due to a voltage level of the video signal.
Furthermore, the above-mentioned configuration of the conventional detection circuit has a drawback that it needs external resistors, resulting in an increase of numbers of components.